Vitamin K Supplements Improve Glucose Tolerance in Men

Increasing research has pointed to the importance of vitamin K in maintaining normal glucose tolerance – i.e., resistance to diabetes. Now, researchers at Tufts University have found that modest supplemental amounts of vitamin K do in fact improve several markers of glucose tolerance.

Sarah Booth, PhD, and her colleagues gave 355 men and women, ages 60 to 80 years old, either 500 mcg of vitamin K1 or placebos daily for three years. By the end of the study, men taking vitamin K had improvements in fasting blood sugar and fasting insulin levels, as well as in the Homeostasis Assessment Model for Insulin Resistance (HOMA-IR). The HOMA-IR is a calculation of insulin resistance based on a combination of fasting blood sugar and insulin.

By the end of the study, men taking vitamin K had decreases in HOMA-IR and fasting insulin – indicating improved glucose tolerance – whereas men taking placebos experienced increases. Men taking vitamin K had a slight increase in fasting blood sugar, but men taking placebos had a four-fold greater increase.

Vitamin K did not influence glucose tolerance in women.

Last year, researchers at Columbia University discovered that the protein osteocalcin also functioned as a hormone regulating glucose tolerance. Vitamin K is needed to activate osteocalcin.

Reference: Yoshida M, Jacques PF, Meigs JB, et al. Effect of vitamin K supplementation on insulin resistance in older men and women. Diabetes Care, 2008; epub ahead of print.